33.8 GHz CCS Survey of Molecular Cores in Dark Clouds

We have conducted a survey of the CCS $J_N = 3_2-2_1$ line toward 11 darkclouds and star-forming regions at 30 arcsec spatial resolution and 0.054 km/svelocity resolution. CCS was only detected in quiescent clouds, not in activestar-forming regions. The CCS distribution shows remarkable clumpy structure,and 25 clumps are identified in 7 clouds. Seven clumps with extremely narrownonthermal linewidths < 0.1 km/s are among the most quiescent clumps everfound. The CCS clumps tend to exist around the higher density regions traced byNH_3 emission or submillimeter continuum sources, and the distribution is notspherically symmetric. Variation of the CCS abundance was suggested as anindicator of the evolutionary status of star formation. However, we can onlyfind a weak correlation between N(CCS) and $n_{H_2,vir}$. The velocitydistributions of CCS clouds reveal that a systematic velocity pattern generallyexists. The most striking feature in our data is a ring structure in theposition-velocity diagram of L1544 with an well-resolved inner hole of 0.04 pcx 0.13 km/s and an outer boundary of 0.16 pc x 0.55 km/s. Thisposition-velocity structure clearly indicates an edge-on disk or ring geometry,and it can be interpreted as a collapsing disk with an infall velocity$\gtrsim$ 0.1 km/s and a rotational velocity less than our velocity resolution.Nonthermal linewidth distribution is generally coherent in CCS clouds, whichcould be evidence for the termination of Larson's Law at small scales, $\sim$0.1 pc.Comment: 21 pages, 25 ostscript figures, accepted for publication in the Supplement Series of the Astrophysical Journal (May 2000